Réduire le nombre de blocks réservés à l’utilisateur root sur un système de fichier ext, et récupérer ainsi l’espace libre pour les utilisateurs.
On ext (ext2, ext3, ext4) filesystems, 5% of the blocks are reserved by default for the root user. For a 1To disk, it represents 50Go. It can safely be reduced.
$ sudo tune2fs -l /dev/mapper/machine--vg-root | rg "Reserved block count" (1)
Reserved block count: 6220910 (2)
$ df -h | rg "machine--vg-root" (3)
/dev/mapper/machine--vg-root 469G 361G 84G 81% /
$ sudo tune2fs -m 0.1 /dev/mapper/machine--vg-root (4)
tune2fs 1.45.5 (07-Jan-2020)
Setting reserved blocks percentage to 0.1% (124831 blocks)
$ python -c 'print(124831*4096/1024)' (5)
499324
$ df -h | rg "machine--vg-root" (6)
/dev/mapper/machine--vg-root 469G 361G 108G 77% /| 1 | Find how many blocks are reserved on your ext partition, here it’s around 25Go (for a 512 Go SSD). |
| 2 | To get the block size : tune2fs -l /dev/mapper/machine—vg-root | rg "Block size" ; here it’s 4096 octets. It can also been read via blockdev --getbsz /dev/mapper/machine—vg-root. |
| 3 | Check the free space of this partition (here it’s 84 Go) |
| 4 | Set the reserved blocks percentage to : 0.1 % |
| 5 | Compute the size in kilo-octects, it’s now around 500 Mo |
| 6 | Check the free space of this partition again, it’s now 108 Go |
| You need to keep some reserved blocks on your root filesystem, else you might brake your system. |
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